Sumo Andromeda power amplifier Sumo Andromeda III in May 1996

Thomas J. Norton reviewed the Sumo Andromeda III in May 1996 (Vol.19 No.5):

Volume VII of Stereophile. That's a long way back. The Orwellian year of 1984, to be specific, and it was in Vol.7 No.6 that we reviewed the original Sumo Andromeda. Back when a home computer meant an Apple II (remember Apple?). Back when Home Theater meant Uncle Bill doing Karaoke without the oke (it hadn't been invented yet).

There's nothing like staying power. Apple is now an endangered fruit, and Uncle Bill still can't remember the words to "Lolly Pop," but the Sumo Andromeda lives on. Now in its third generation, the Andromeda III is, like its predecessors, a solid performer at a fair price. In a high-end audio world increasingly dominated by sticker shock, the newest Andromeda, at $1799, will cost you just $300 more than the Andromeda II that I reviewed in 1991 (Vol.14 No.6).

Sumo says that the internal topology of the Andromeda III is largely new, though most of the main design features of the amp remain the same. As with the original, the Andromeda III's main technical bragging ground is its fully balanced design. That is, it is balanced all the way through, from input to output (though unbalanced inputs are also provided). The positive and negative output terminals are both actively driven. Since the negative output terminals are not at ground potential, the negative terminals of the two channels must never be connected together. Neither must they be connected to the system ground. Otherwise, to quote JA as he walks past while I am bench-testing some high-power amplifier or other: "BANG!"

If you add any type of network, such as a multiple loudspeaker switcher, between the amplifier outputs and the loudspeakers, you must ensure that this device never straps the two channel grounds together nor connects them to any other ground. In practice, this is irrelevant for the typical user driving a single pair of loudspeakers. But it is an important consideration for those with custom installations. Furthermore, the two channels of the Andromeda cannot be bridged.

To make full use of the Sumo's balanced topology, two forms of balanced inputs are provided: positive and negative RCA, and XLR. When the amp is to be driven single-ended, the positive RCA jacks are used and shorting plugs are inserted into the negative jacks.

As is usual for a power amplifier, all of the Sumo's low-level gain stages are operated in class-A. The output stages have sufficient bias current to operate in class-A at low power, transitioning to class-AB as the power demand increases. Sumo's proprietary "TL" circuit (Transconductance Linearization) compares the gate and source voltages of the output MOSFETs and provides error correction to the driver stage as required. The TL circuit also provides the bias for the output devices. There is no overall (global) feedback. Power is supplied by a single 1500VA transformer with 50,000µF of filter capacitance. A total of 16 MOSFETs are used in the output stage.

In its physical design and ergonomics, I found the Andromeda III as attractive as it needs to be, but its price is not inflated by expensive cosmetics (footnote 1) (the styling is identical to that of Andromeda II). The back panel, however, is crowded. There is the line-cord input, five fuse holders (two rail fuses per channel and the main power supply fuse), four RCA jacks, and two XLR jacks jockeying for position. I wish there were another, duplicate set of output jacks—to facilitate bi-wiring with some cables—but there is nowhere they could go!

There's no doubt that the trend in amplifiers in recent years has been toward smoothness, sweetness, and warmth, sometimes at the expense of detail and clarity. Could this be because reviewers in general tend to prefer this type of sound? Or because of the high-end popularity of tube amplifiers? To many audiophiles, an abundance of detail sounds suspiciously like "hi-fi," or even "digital" or "solid-state." Something Wicked This Way Comes.

I take no holier-than-thou stance here, and have certainly leaned in this direction as much as the next reviewer (though I am definitely neither anti-digital nor anti–solid-state). Yet I have always delighted in the proper reproduction of detail. If it isn't in-your-face or clearly too-bright or etched, detail adds undeniable life to the sound. Live music is full of detail.

And the Sumo Andromeda III has it. Lotsa detail. Clarity to spare. I hear none of Sam Tellig's classic "MOSFET Mist" here. If we limit our vocabulary to "bright" and "dark," the Sumo would have to be described as "bright." But that term is insufficient here—and misleading. Say "bright" to an audiophile and he or she thinks "etched," "edgy," "unpleasant," or even "strident." The Andromeda is none of those things, though there would be no confusing it with a tube amplifier save for one aspect—its sense of life and immediacy. There is, subjectively, a subtle forwardness in the Sumo's upper midrange and low treble, that crisply defines images in space. Vocals sound clear and vibrant. The textures of voices are clearly rendered. Tiny details, such as the buzz of guitar strings, the snap of percussion, are all there. There is a trace of a metallic quality to the sound that I do not hear with a number of other good amplifiers. However, I cannot clearly trace this to the Sumo—it could just as easily be blamed on the recordings, or on the metal-dome midrange and tweeter on the Veritas.

It seemed, in fact, as though the Sumo was merely telling it like it is. Good recordings sounded stunning. "Jersey Girl" and, in particular, "Train Song," from a limited-edition Holly Cole sampler released by Energy Loudspeakers (footnote 2) (Sound as a Performance Art, Alert DPRO-313) had a clarity, precision, and "alive" quality that are only too rarely heard in reproduced sound. "Veiling" is not a word that comes to mind here. The subtle detailing on "Train Song" sparkled; the bells at 2:45 into the cut were clearly distinguishable as individual sounds, and I could almost make out the words uttered by the instrumentalists at the end of the song. And while questionable recordings can sound analytically crisp with the Andromeda, I never found any recording of reasonable quality to sound irritating or over-the-top.

The general sparkle and detail of the Andromeda is enhanced by a tight, well-defined, punchy bottom end. The mid and upper bass sound a little lean compared with warmer-sounding amplifiers, but on the Veritas—itself a little overwarm—the match was ideal. Male vocals were refreshingly free of that slight trace of plumpness—inaccurate though often pleasant—which is a problem with many large loudspeakers, including the Energys. Instrumental bass was as tight as I have ever heard it over the Veritas 2.8 loudspeakers. The bass extension on the soundtracks from Jumanji (Epic EK67424) and Patriot Games (RCA 07863 66051-2) was exceptional. The ubiquitous, percussive whacks on the latter in particular were a little less explosively full-bodied than I have heard with other amps, but made up for it in tightness and punch. And the double bass on the above-mentioned Holly Cole album was in-the-room real.

The soundstaging from the Andromeda III was first-rate, with a see-through transparency that greatly enhanced the sense of reality. Lateral focus was precise; depth was convincing. The midrange was clear and open. While vocals were very much present, the slight coolness to the sound—a result of the otherwise-desirable top-end sparkle and midbass tightness—made them less palpably rich than with warmer, more full-bodied-sounding amplifiers. I would have occasionally preferred a bit more warmth, but not if it meant sacrificing any of the Andromeda's positive qualities.

All of the above observations were made with the Andromeda driven from its unbalanced inputs. I am not a particular fan of balanced interconnects for home audio, except in special cases where noise pickup in the cables might be a problem. In my system and listening room, I have only rarely heard any sonic improvement—and then quite subtle—from using the balanced mode. Certainly the differences have been nowhere near those heard, for example, with different cables. While XLR connectors are definitely an improvement on the standard RCA plug, balanced mode has always struck me as an increased cost to all buyers that only benefits a few. Despite the Sumo Andromeda's fully balanced internal topology which might argue intuitively for superior sound from a balanced input, I could not decisively pin down any sonic benefit from a balanced connection in my system.

While I thought that perhaps—just perhaps—I may have heard a subtly softer sound from the balanced connection, the difference was elusive and not worth agonizing over. My balanced preamp-to-power amp interconnects are about 5' longer than the similar Cardas Hexlinks I used for the unbalanced run. This alone could possibly account for the slight difference I might have heard. If you are using a preamp with a balanced output, I certainly see no disadvantage in driving the Andromeda III balanced. But if you do not, you have no reason to feel deprived in the sound you might expect from the Sumo. For the remainder of my listening, I continued using the unbalanced input.

First up, the $3995 Carver Research Lightstar Reference. I have used the Carver frequently in recent months with the Energy loudspeakers, and have been captivated by the combination. Clearly, the Carver/Energy match is rather rich-sounding, but the clear, palpable midrange and sweet top end have never disappointed me. The Sumo/Energy offers a entirely different sound. The added tightness of the Sumo noticeably opens up the soundstage; its more detailed top end adds sparkle. Surprisingly, I found that though the Sumo is crisper-sounding than the Carver, the latter is slightly dryer and grainier in the sibilance region.

While I preferred the Carver on some material for that vivid-yet-sweet midrange, more often the tight clarity of the Sumo won me over. On "Superman's Song," from the Crash Test Dummies' The Ghosts that Haunt Me (Arista ARCD-8677), for example, the Carver took the honors. The Sumo was a little lean and cool-sounding here. This is hardly a natural recording—though a very good one—and it could easily be argued that the leaner sound of the Sumo was more true to what is on the disc. Absent a direct comparison, the Sumo sounded excellent. With both amplifiers on hand, the extra warmth of the Carver won out.

But on the King's Singers' Good Vibrations (RCA 60938-2), the added warmth from the Lightstar simply muddled the voices. The Carver is decidedly darker-sounding than the Sumo, and some will prefer it for that reason, but I welcomed the extra clarity and snap from the Andromeda III. The same was true on Potato Radio (Justice Records JR#0802-2). The latter displayed a sense of focus with the Sumo that the sweeter, yet slightly more homogenized, sound of the Carver could not equal.

And Holly Cole's "Train Song" through the Carver—with its richer and somewhat more powerful bass and vocal immediacy and sweetness—could not be judged anything but excellent. Yet it sounded veiled next to the precise, detailed, sheer "liveness" of the Sumo.

I also had the opportunity to briefly compare the Sumo to the recently discontinued Krell KSA-300S. Surprisingly, the Andromeda was more effective on some material. On Jumanji, the deep bass was more constrained with the Krell. It is perhaps this very quality that allows the KSA-300S to tightly control the bass performance of so many loudspeakers, but on the Energys, I couldn't deny that the bass from the Andromeda sounded more powerful and unrestrained. The crispness of the Sumo also leant a more sharp-edged definition to the sound, compared with the more relaxed, sweeter sound of the Krell.

On the other hand, though the Krell's balance in the upper midrange/low treble was quite similar to that of the Sumo, the Krell's more rounded weight in the upper bass/lower midrange better balanced out this upper mid/low treble immediacy, and gave it the upper hand in providing full, natural reproduction of voices and solo instruments.

Yet I couldn't deny that on some material I had to give the Sumo the nod over the Krell. The former did, at times, sound more focused and transparent. Does this mean that the Andromeda III is the better amp? It would be foolish to leap to that conclusion. The Krell has proved its value over the long haul with a wide range of loudspeakers (see, for example, my recent reviews of the Wilson WITT and the KEF Reference Series Model Four). And the Krell is designed to be bulletproof into virtually any load. But the Andromeda III was not sent packing by the Krell. It definitely surprised me here, and more than held its own. Which simply reminds us that when comparing two up-to-date, technically competent amplifiers driving a given loudspeaker, your ears should be your guide.

My reaction to the Sumo Andromeda III is not substantially different from my reaction to its predecessor. When I went back and reread my own review of the Andromeda II (after I finished the above review) I was not surprised by my earlier words. "The low end sounded powerful and gutsy...the top end was open and airy, with a definite but not overdone sparkle...nothing hazy or misty about the Sumo's top-end...," and "Somewhat lean in the lower midrange." Even making allowances for an entirely different reference system and room, I could have written any of this today about the Andromeda III. Does the Sumo Andromeda III sound exactly the same as the II? While we haven't had a II in-house for years, there is definitely a family resemblance reflected in my respective reviews. But my feeling now is that, appropriately matched with the right loudspeaker, the Andromeda III definitely can elbow its way into class B. It is a terrific amplifier at what is nearly a bargain price.—Thomas J. Norton

Footnote 1: Makers of super high-end amplifiers are often faced with a Catch 22. Their amps have to be expensive because of the expensive design and parts content. To justify this expense, deluxe cosmetics must be added, which raises the price even further. The chassis and front panel of such amplifiers may well be their most expensive components.

Footnote 2: Both songs are also available on Holly Cole's album Temptation (Alert 81026/Metro Blue/Capitol 31653).